Running PHPUnit tests

Problem/Motivation

I've followed the steps in this tutorial: https://mglaman.dev/blog/running-drupals-phpunit-test-suites-ddev but I'm finding my test always fails as the database connection used when drupalGet() is called is missing the `test{TEST_ID}` prefix and so the get is run against the main database tables and not the test ones.

First off this is the require-dev section of my `composer.json` file:

"require-dev": {
        "dealerdirect/phpcodesniffer-composer-installer": "^0.7.0",
        "drupal/core-dev": "8.8.8"
    },

I've copied the `core/phpunit.xml.dist` file to my docroot and have renamed to `phpunit.xml`

<?xml version="1.0" encoding="UTF-8"?>

<!-- TODO set checkForUnintentionallyCoveredCode="true" once https://www.drupal.org/node/2626832 is resolved. -->
<!-- PHPUnit expects functional tests to be run with either a privileged user
 or your current system user. See core/tests/README.md and
 https://www.drupal.org/node/2116263 for details.
-->
<phpunit bootstrap="web/core/tests/bootstrap.php" colors="true"
         beStrictAboutTestsThatDoNotTestAnything="true"
         beStrictAboutOutputDuringTests="true"
         beStrictAboutChangesToGlobalState="true"
         printerClass="\Drupal\Tests\Listeners\HtmlOutputPrinter">
  <php>
    <!-- Set error reporting to E_ALL. -->
    <ini name="error_reporting" value="32767"/>
    <!-- Do not limit the amount of memory tests take to run. -->
    <ini name="memory_limit" value="-1"/>
    <!-- Example SIMPLETEST_BASE_URL value: http://localhost -->
    <env name="SIMPLETEST_BASE_URL" value="http://localhost"/>
    <!-- Example SIMPLETEST_DB value: mysql://username:password@localhost/databasename#table_prefix -->
    <env name="SIMPLETEST_DB" value="mysql://db:db@db/db"/>
    <!-- Example BROWSERTEST_OUTPUT_DIRECTORY value: /path/to/webroot/sites/simpletest/browser_output -->
    <env name="BROWSERTEST_OUTPUT_DIRECTORY" value="sites/simpletest/browser_output"/>
    <!-- To have browsertest output use an alternative base URL. For example if
     SIMPLETEST_BASE_URL is an internal DDEV URL, you can set this to the
     external DDev URL so you can follow the links directly.
    -->
    <env name="BROWSERTEST_OUTPUT_BASE_URL" value=""/>
    <!-- To disable deprecation testing completely uncomment the next line. -->
    <!-- <env name="SYMFONY_DEPRECATIONS_HELPER" value="disabled"/> -->
    <!-- Example for changing the driver class for mink tests MINK_DRIVER_CLASS value: 'Drupal\FunctionalJavascriptTests\DrupalSelenium2Driver' -->
    <env name="MINK_DRIVER_CLASS" value=''/>
    <!-- Example for changing the driver args to mink tests MINK_DRIVER_ARGS value: '["http://127.0.0.1:8510"]' -->
    <env name="MINK_DRIVER_ARGS" value=''/>
    <!-- Example for changing the driver args to phantomjs tests MINK_DRIVER_ARGS_PHANTOMJS value: '["http://127.0.0.1:8510"]' -->
    <env name="MINK_DRIVER_ARGS_PHANTOMJS" value=''/>
    <!-- Example for changing the driver args to webdriver tests MINK_DRIVER_ARGS_WEBDRIVER value: '["chrome", { "chromeOptions": { "w3c": false } }, "http://localhost:4444/wd/hub"]' For using the Firefox browser, replace "chrome" with "firefox" -->
    <env name="MINK_DRIVER_ARGS_WEBDRIVER" value=''/>
  </php>
  <testsuites>
    <testsuite name="unit">
      <file>./tests/TestSuites/UnitTestSuite.php</file>
    </testsuite>
    <testsuite name="kernel">
      <file>./tests/TestSuites/KernelTestSuite.php</file>
    </testsuite>
    <testsuite name="functional">
      <file>./tests/TestSuites/FunctionalTestSuite.php</file>
    </testsuite>
    <testsuite name="functional-javascript">
      <file>./tests/TestSuites/FunctionalJavascriptTestSuite.php</file>
    </testsuite>
    <testsuite name="build">
      <file>./tests/TestSuites/BuildTestSuite.php</file>
    </testsuite>
  </testsuites>
  <!-- Filter for coverage reports. -->
  <filter>
    <whitelist>
      <directory>./includes</directory>
      <directory>./lib</directory>
      <!-- Extensions can have their own test directories, so exclude those. -->
      <directory>./modules</directory>
      <exclude>
        <directory>./modules/*/src/Tests</directory>
        <directory>./modules/*/tests</directory>
      </exclude>
      <directory>../modules</directory>
      <exclude>
        <directory>../modules/*/src/Tests</directory>
        <directory>../modules/*/tests</directory>
        <directory>../modules/*/*/src/Tests</directory>
        <directory>../modules/*/*/tests</directory>
      </exclude>
      <directory>../sites</directory>
    </whitelist>
  </filter>
</phpunit>

And I'm running the below test by running:

`../vendor/bin/phpunit -v -c ../phpunit.xml path-to-module`

namespace Drupal\Tests\custom_module\Functional;

use Drupal\node\Entity\Node;
use Drupal\Tests\BrowserTestBase;

/**
 * Test the sidebar displays what we expect
 *
 * @group custom
 */
class RelatedPagesTest extends BrowserTestBase
{
  /**
   * The modules to load to run the test.
   *
   * @var array
   */
  public static $modules = [
    'field',
    'node',
    'taxonomy',
    'custom_module',
  ];

  /**
   * {@inheritdoc}
   */
  protected function setUp() {
    parent::setUp();
  }

  public function testRelatedPagesDoesntShowWhenNoContent()
  {

    $news = $this->container->get('entity_type.manager')->getStorage('node')
      ->create([
        'type' => 'news',
        'title' => 'News article without sidebar',
      ]);
    $news->save();

    $this->drupalGet('node/' . $news->id());
    $this->assertSession()->statusCodeEquals(200);

    // Assert sidebar is missing completely
    $this->assertText('News article without sidebar');
    $this->assertNoText('Show me more');
  }
}

With a TON of debug I can see the following is happening:

• The database connection is taken from `phpunit.xml` and sets that as the db connection
• The test{TEST_ID} table prefix is added to the database configuration
• The simpletest/{TEST_ID} folder is created and this copies the database settings from the default/testing.settings.php *The prefix is missing here*
• The test runs and the node is added to the database. Querying the NIDs within the test gives me one nid of 1
• THIS IS THE STEP THAT GOES WRONG
• The test then calls `$this->drupalGet()` for node/1
• The db connection used doesn't have the table prefix so loads the site node/1 (the homepage)
• The test fails

I've been debugging and I can't figure out why the table prefix gets dropped out of the database connection. Any help is much appreciated!

Cheers

Tom